NL2034462B1

NL2034462B1 - Conductive catalytic particle and method of producing conductive catalytic particles

Info

Publication number: NL2034462B1
Application number: NL2034462A
Authority: NL
Inventors: Sotoodeh Farnaz
Original assignee: Sotoodeh Beheer B V
Priority date: 2023-03-29
Filing date: 2023-03-29
Publication date: 2024-10-04
Also published as: WO2024205414A1; EP4688261A1

Abstract

Conductive catalytic particle for heterogeneous catalysis as well as a method of producing said particles is presented. The method comprises a provision step (Sl) of providing, in a vessel, porous 5 particles comprising a porous support material carrying a catalyst material, and an impregnation step (SS) of exposing, in the vessel, the porous particles to an impregnation solution comprising a conductive polymer in carbon dioxide, thereby impregnating the porous particles with the conductive polymer to obtain the conductive catalytic particles. 10 Figure for publication: FIG. 1

Description

CONDUCTIVE CATALYTIC PARTICLE

AND

METHOD OF PRODUCING CONDUCTIVE CATALYTIC PARTICLES

The present disclosure relates to the technical field of conductive catalytic particles for heterogenous catalysis and methods of producing such particles.

Catalytic particles are used in a wide range of heterogeneous catalysis applications. Electrical conductivity of the catalytic particles is of importance in various electrochemical applications, such as electrolysis and fuel cells. Conductive catalytic particles are known for such applications.

However, there is a need to improve existing technologies to ensure more sustainable processes.

The present disclosure provides improved conductive catalytic particles and methods of producing these, in particular regarding catalytic efficiency.

An aspect of the disclosure provides a method of producing conductive catalytic particles for heterogeneous catalysis. The method comprises a provision step of providing, in a vessel, porous particles comprising a porous support material carrying a catalyst material; and an impregnation step of exposing. in the vessel, the porous particles to an impregnation solution comprising a conductive polymer in carbon dioxide, thereby impregnating the porous particles with the conductive polymer to obtain the conductive catalytic particles.

This method offers a relatively uncomplicated method to produce conductive catalytic particles from various porous particles which comprise a porous support material carrying a catalyst material. Various materials are suitable for the porous support material and the catalyst material. It is therefore a versatile method.

The impregnation step may comprise controlling temperature and pressure in the vessel to have the carbon dioxide of the impregnation solution in a liquid or supercritical state. In other words, the impregnation step may be performed with liquid or supercritical carbon dioxide. Preferably, the carbon dioxide of the impregnation solution is in the supercritical state for the impregnation step.

For example, a solution of the conductive polymer can be pumped into the vessel while the carbon dioxide is in liquid form, to be brought in the supercritical state once in the vessel by increasing temperature and/or pressure. In addition to the carbon dioxide of the impregnation solution, the impregnation solution as a whole may be in a liquid or supercritical state, when pumped into the vessel.

The method may further comprise a drying step of drying the obtained conductive catalytic particles. The drying step thus follows the impregnation step. The drying step serves to release the carbon dioxide and any co-solvent from the vessel and can be implemented in various ways, for example by purging and/or by depressurizing the vessel.

The provision step may comprise a synthesis step of providing the porous support material in the vessel and exposing the porous support material in the vessel to a catalyst impregnation solution, preferably comprising the catalyst material in carbon dioxide, thereby producing the porous particles comprising the porous support material carrying the catalyst material. Though itis preferred that the porous particles are synthesized in the same vessel also used for the impregnation step, the porous particles may also be synthesized in another vessel before being transferred into the vessel in which the impregnation step is performed. The porous particles carrying a catalyst material may be readily available at the start of the method. For example, commercially available catalysts in the form of porous particles can be improved with the method, in particular the impregnation step, as presently disclosed.

The synthesis step may comprise controlling temperature and pressure in the vessel to have the carbon dioxide of the catalyst impregnation solution in a liquid or supercritical state. The carbon dioxide may thus be liquid or supercritical in both the impregnation step as well as the synthesis step. It is preferred that the carbon dioxide is supercritical in at least one of these two steps, or even in both of these steps. As both the synthesis step and the impregnation step can be performed using carbon dioxide in liquid or supercritical state, and preferably in supercritical state, both the synthesis step and the impregnation step can be performed in the same vessel, thus providing a single reactor (vessel) method in the manufacture of conductive catalytic particles for heterogeneous catalysis.

The provision step may comprise an activation step of activating the catalyst material carried by the porous support material in the porous particles. The activation step may comprise calcination or reduction of the catalyst material carried by the porous support material in the porous particles.

Activation, such as by calcination or reduction, may improve the catalytic activity of the catalyst material with respect to a particular reaction that is to be performed by the conductive catalytic particles. Examples include water splitting and fuel cell reactions.

Heterogeneous catalysts are typically supported, which means that the catalytic material is dispersed in, on and/or through the porous support material. Supports prevent or minimize agglomeration and sintering of small catalyst particles and thus exposing more surface area, resulting in an increased specific activity of the catalytic material carried by the porous support compared to the catalytic material without the porous support. Various materials can be employed for the porous support material. The porous support material may be formed from a porous carbon, preferably in the form of activated carbon or graphene. Further, the porous support material may be formed from a porous metal oxide, preferably, but not limited to, selected from a group comprising silica, alumina, zinc oxide and cerium oxide. Said porous metal oxides may comprise silicon, aluminium, zinc, tin, cerium, one or more transition metals such as titanium and zirconium, or combinations thereof. Finally, the porous support material may be formed from a porous inorganic material.

The choice of catalyst material, just like the choice of porous support material, is not critical to the method. The catalyst material may be a metal-based catalyst, for example comprising Pt, Pd or Ni.

As for the conductive polymer, the term is meant to refer to intrinsically conductive polymers, which are organic polymers that conduct electric charge, for example in the form of electrons, protons, hydroxide or other ions. It includes polyelectrolytes, ionenes and ionomers.

It is preferred that the conductive polymer is an ionomer, which may in particular be selected from

Anion Exchange lonomers (AEls} or Cation Exchange lonomers (CEIs) typically used in the manufacture of membrane separators in electrochemical cells. The ionomer may for example be a sulfonated tetrafluoroethylene based fluoropolymer-copolymer or a sulfonated poly-styrene based material. Examples of current state-of-the-art AEls are the benzyltrimethylammonium- functionalized poly(ethylene-co-tetrafluoroethylene) (BTMA-ETFE) ionomers, polyfluorene (FLN) ionomers, poly(terphenyl piperidinium) (PTP) ionomers, poly(biphenyl piperidinium) (PBP) ionomers. An example of a current state-of-the-art CEL is perfluorosulfonic-acid (PFSA).

The composition of the impregnation solution may be chosen based on the conductive polymer to be impregnated into the porous particles. The impregnation solution may further comprise a co- solvent miscible with the conductive polymer and carbon dioxide under process operating conditions in the vessel. A co-solvent may improve solubility of the conductive polymer in liquid or supercritical carbon dioxide. The type and quantity of a co-solvent are generally selected depending on conductive polymer and reaction conditions. Examples of relevant cosolvents include water and alcohols, preferably a C1, C2 or C3 alcohol such as methanol, ethanol and iso- propanol.

The method advantageously allows the same vessel to be used for its various steps. A single vessel suffices to produce conductive catalytic particles merely requiring, in the simplest form of the method, the porous particles, the conductive polymer and carbon dioxide. Synthesis of the porous particles can be performed in the same vessel using, as a minimum, the porous material and the catalyst material in addition to the aforementioned material. The same source of carbon dioxide can be used for both the synthesis step and the impregnation step.

Another aspect of the disclosure provides a conductive catalytic particle for heterogeneous catalysis, obtainable by the methods as disclosed herein.

Conductive catalytic particles obtained by the method, in particular via the impregnation step thereof, exhibit improved characteristics, for example in relation to electrical conductivity and/or increased catalytic performance compared to conductive catalytic particles produced using a conventional method of impregnations (such as by sonication).

The inventors have also observed improvements in shape, morphology and/or size of the conductive catalytic particles obtained by the method, which are more rounded and/or more monodisperse than can be obtained by impregnation based on conventional sonication techniques.

The conductive catalytic particle may comprise a porous support material, a catalyst material and a conductive polymer. The catalyst matertal is in particular carried by the porous support material and the conductive polymer is impregnated into the porous particle formed by the porous support material carrying the catalyst material.

The porous support material, the catalyst material and the conductive polymer can be formed of any of the materials given above.

The conductive catalytic particle as disclosed herein may be characterized by various parameters, including the following.

The conductive catalytic particle may have a cross-sectional size in the range of from 0.1 pm to 1-10? um, preferably from 1 pum to 1-10? um, more preferably from 1 um to 50 um, as measured by electron microscopy. In particular, scanning electron microscopy or transmission electron microscopy can be employed.

The conductive catalytic particle may have a cross-section with a roundness in the range of from 0.3 to 1, preferably from 0.5 to 1, more preferably from 0.7 to 1. The definition of roundness used herein is the ratio of the radii of inscribed and circumscribed circles of the shape under consideration. The inscribed radius and circumseribed radius refer to the maximum and minimum 5 sizes for circles that are just sufficient to fit inside or to enclose the cross-sectional shape of the particle, respectively. This is also known as the ISO definition of roundness and ranges from 0 (not round at all) to 1 (shape of a circle). Roundness is computed as r/ R with r being the inscribed radius and R being the circumscribed radius of the shape under consideration as measured by electron microscopy.

Another aspect of the disclosure provides a catalytic formulation comprising conductive catalytic particles as disclosed herein. The catalytic formulation may further include a liquid phase in addition to a particulate phase formed by the conductive catalytic particles. The liquid phase may be formulated for the intended use of the catalytic formulation and may include (remnants of) the co-solvent used in the impregnation step. The catalytic formulation may be a catalytic ink, in particular suitable for coating onto membranes for electrochemical cells to obtain what are known as catalyst-coated membranes (CCM).

Another aspect of the disclosure provides catalyst-coated membranes comprising a membrane having at least one face provided with conductive catalytic particles as disclosed herein. The catalyst-coated membranes can be obtained by the application of the conductive catalytic particles obtained using the methods of the invention onto a membrane, in particular a ceramic or a polymer membrane, using a catalytic formulation as disclosed herein, e.g. in the form of a catalytic ink.

Techniques to apply such catalytic ink include ink-jetting, sputtering, spin-coating and the like.

Conductive catalytic particles of a first type may be coated on a first face of the membrane, while conductive catalytic particles of a second type may be coated on a second face of the membrane. In other words, both sides of the membrane may be coated with different conductive catalytic particles.

No separate binder is needed to couple the conductive catalytic particles to the surface of the membrane, as the conductive polymer, in particular in the form of an ionomer, performs the function of binder.

In a particular aspect the catalyst-coated membrane may have a membrane that is formed with a conductive polymer corresponding to the conductive polymer of the conductive catalytic particle.

Here, the term corresponding refers to the conductive polymers being identical, but may also mean that these have at least common monomers, common blocks of co-polymers, or common side chains. In said instance where the membrane is formed with a conductive polymer corresponding to the conductive polymer of the conductive catalytic particle, the binding of the conductive catalytic particles to the surface of the membrane was found to be enhanced.

Another aspect of the disclosure provides an electrochemical cell comprising two electrodes separated by a catalyst-coated membrane as disclosed herein.

Improvements in electrochemical performance have been observed when the conductive catalytic particles obtained by the method are used to coat membranes of an electrochemical cell, in particular an electrolytic cell.

The electrochemical cell may be a fuel cell, an electrolytic cell or an electrolyzer, for example.

A final aspect of the disclosure presents uses of the conductive catalytic particles as disclosed herein in the manufacturing of a heterogeneous catalytic material, a catalytic formulation, a catalytic ink, a catalyst-coated membrane and/or an electrochemical cell.

The description following below with the associated figures further address aspects of the present disclosure. In the figures:

FIG. | shows a schematic illustration of a catalyst particle;

FIG. 2 shows a schematic illustration of an electrochemical cell with a catalyst-coated membrane;

FIGS. 3A-3B show electron microscopy images of conductive catalytic particles obtained by a method according to a comparative example (FIG. 3A) and by a method according to the present disclosure (FIG. 3B), respectively:

FIGS. 4A-4B show particle size distribution diagrams of the particles imaged in FIGS. 3A-3B;

FIG. 5 shows electrochemical test results of the particles imaged in FIGS. 3A-3B;

FIG. 6 shows a reactor design for producing conductive catalytic particles; and

FIG. 7 shows a flow diagram of a method of producing conductive catalytic particles.

The following reference signs are used: 10 conductive catalytic particle 11 porous support material 12 catalyst material 13 porous particle

14 conductive polymer 20 catalyst-coated membrane 21 polymer membrane layer 22 first face of membrane 23 second face of membrane 24 first catalyst coating, composition or ink 25 second catalyst coating, composition or ink 30 electrochemical cell 31 first half-cell 32 second half-cell 33 first connection (e.g. cathode) 34 second connection (e.g. anode) 35 power source (e.g. voltage supply) 40 reactor 41 vessel 42 openable cover 43 stirrer 44 vanes 45 drive 46 infeed 47 outlet

Si provision step

S2 synthesis step

S3 purging step

S4 activation step

S5 impregnation step

S6 drying step

In FIG. 1, a schematic and even cartoon-like illustration of a conductive catalytic particle 10 is shown. It shows a porous support material 11 with therein a distribution of catalyst material 12.

The dark lines represent a well-distributed network of conductive polymer 13 within the conductive catalytic particle. Notable in this cartoon-like presentation of a conductive catalytic particle 10 according to the invention is its overall round (sphere like) shape, shown to be a result of the impregnation method according to the invention, and found to improve the catalyst activity of the thus obtained materials (see Figure 5 below).

The conductive catalytic particles may find use in various applications. An example is shown in

FIG. 2, which presents a schematic illustration of an electrochemical cell 30 comprising a catalyst coated membrane 20 obtained by applying a catalytic formulation (ink) 24, 25 comprising conductive catalytic particles 10 as herein disclosed at either face 22, 23 of a polymer membrane 21. As mentioned before, the catalytic formulation at either side of the membrane could be the same or different, that is in particular the same or different in relation to the conductive catalytic particles 10 present in said catalytic formulations. Bach side of the membrane corresponds to the catalytic phase of a respective first 31 and second 32 half-cell of the electrochemical cell, with in the shown cell 30 at the cathode side 33 the formation of hydrogen (Hs) and at the anode side 34 the formation of oxygen (Oz) from water (H20) fed into the cell via the polymer membrane 21, when an electrical power source 35 (e.g. voltage) is being applied. It is noted that the catalyst- coated membrane 20 may also be provided with a catalyst coating on only one of its faces 22, 23.

FIGS. 3A-3B show electron microscopy images of conductive catalytic particles obtained by a method according to a comparative example and by a method according to the present disclosure, respectively. In the comparative example the same porous support material carrying a catalyst material is impregnated with an impregnation solution comprising the same conductive polymer, by means of sonication instead of the carbon dioxide-based impregnation step of the present invention. The electron microscopy images clearly show a difference in the morphology of the conductive catalytic particles. Note the difference in scale. With the impregnation by sonication (Figure 3A) larger particles are obtained, and these particles are irregular in shape. This in contrast to the impregnation by means of liquid or saper-critical carbon dioxide, resulting in smaller and more spherically shaped particles. Image analysis of FIG. 3B provides roundness values in the range of 0.7 — 0.9. Therefore, and using the method of the present invention the active surface area of the conductive catalytic particles is significantly increased.

To underscore the above, FIGS. 4A-4B show particle size distribution diagrams of the particles imaged in FIGS. 3A-3B. lt nicely confirms the visual observation of the electron microscopy images with a narrower size distribution for the conductive catalytic particles obtained by the method of the invention. Compared to the impregnation by sonication, the particles of the invention have an average particle size in the single digit um size, in particular from about 2 to about 6 um.

FIG. 5 shows comparative electrochemical test results of the particles imaged in FIGS. 3A-3B.

The voltage vs. current density graph presents the reduction of electrolysis cell potential for the catalyst particles obtained according to invention when compared to conventional particles. This is advantageous because a lower voltage is needed to obtain the same current density for electrolysis to take place (i.e. the catalyst of the invention makes the system more efficient). Expressed differently, given the higher active surface area the conductive catalytic particles obtained by a method according to the invention are more efficient in their catalytic activity.

FIG. 6 shows a reactor 40 design for producing conductive catalytic particles with the method as herein provided. In its simplest form, the reactor consists of a vessel 41, comprising stirring means, here represented by a stirrer 43 with drive means (motor) 45 and vanes 44. The method being performed in the presence of liquid and preferable supercritical carbon dioxide, the reactor vessel 41 needs to be closed, preferably with an openable cover 42, enabling pressurizing of the reactor vessel when fed via an inlet 46 with the impregnation solution and/or catalyst impregnation solution. Outlet 47 enables venting of the carbon dioxide (CO:2) and eventual co-solvents at the end of the procedure or between process steps where needed. At the start, the vessel 41 is filled with non-conductive catalytic particles. The vessel is closed, fed with the impregnation solution comprising liquid carbon dioxide (CO:} and the conductive polymer 14, optionally in the presence of a co-solvent. The pressure and temperature in the vessel are controlled such that at least the carbon dioxide (CO:), and preferably the whole impregnation solution is in a supercritical phase.

Stirring the non-conductive catalytic particles in such environment results in the impregnation of the particles with the conductive polymer, yielding the conductive catalytic particles 10 according to the invention.

The provision step S1 includes at least the provision of a porous support material carrying a catalyst material into the reactor. As mentioned, the impregnation step can be performed on existing porous support material carrying a catalyst material. in converting such materials into conductive catalytic materials. Alternatively, the provision step includes the actual synthesis of such porous support material carrying a catalyst material, starting from a porous support 11.

In such instance the provision step S1 includes a synthesis step S2 wherein a porous support 11 is fed into the reactor and said material is impregnated with a catalyst impregnation solution. As for the impregnation step S2, this is preferably performed with a catalyst impregnation solution comprising liquid carbon dioxide, wherein the pressure and temperature in the vessel are controlled such that at least the carbon dioxide, and preferably the whole catalyst impregnation solution, is in a supercritical phase. Stirring the porous support particles 11 in such environment results in the impregnation of the particles with the catalyst 12, yielding a porous support material carrying a catalyst material. After purging S3 the reactor to vent the carbon dioxide, the porous support material carrying a catalyst material may undergo a subsequent activation step S4 with a final purging S3.

In order to obtain the conductive catalytic particles 10 according to the invention, the method includes an impregnation step S5 in the reactor of the porous support material carrying a catalyst material provided or obtained in provision step S1, using an impregnation solution comprising liquid carbon dioxide and the conductive polymer 14, optionally in the presence of a co-solvent.

During the impregnation step S53, the pressure and temperature in the vessel are controlled such that at least the carbon dioxide, and preferably the whole impregnation solution, is in a supercritical phase. Stirring the non-conductive catalytic particles in such environment results in the impregnation of the particles with the conductive polymer, yielding after drying (step S6) the conductive catalytic particles 10 according to the invention,

As evident from the foregoing, the purging step S3 includes purging the vessel and may be performed at various stages of the method. For example. purging steps S3 may be performed between the synthesis step S2 and the activation step S4, and/or between the activation step S4 and the impregnation step S35. The drying step S6 may also involve purging, e.g. include a purging step

S3.

EXAMPLE

The following presents an exemplary implementation of the method.

Synthesis step S1

Step S2 & S3. Metal salt impregnation of porous support a. Mix metal salt and porous support in the high-pressure reactor b. Purge reactor from air by passing CO: at 2 — 3 bar for few minutes c. Increase pressure and temperature (up to 200 bar and 200°C) d. Keep for at least 12 — 24h e. Depressurize and reduce temperature

Step S4 & S3. Activation of the metal salt impregnated porous support a. Including heat treatment (calcination) and/or subsequent hydrogen gas treatment (reduction), depending on the oxidation state needed for the active phase (catalyst) with respect to the desired reaction to occur.

al. If calcination is needed, the reactor is heated to between 200 — 300°C (higher might be needed depending on the catalyst, e.g. metal), under the flow of a noble gas or flowing or static air depending on the recipe, for 5 — 10 h. al. Hf reduction is needed, the reactor is under flow of hydrogen gas at a temperature between 100 — 300°C for 2 — 4h. b. Purge under a noble gas (such as helium) to remove byproduct

For example, the purging step S3 between the synthesis step S2 and the activation step S4 or between the activation step S4 and the impregnation step S5 may involve purging the vessel with carbon dioxide for a few minutes under 2 — 5 bar

Impregnation step S5

Phase diagrams are available to determine the conditions in which carbon dioxide is in a liquid or supercritical state. For example, carbon dioxide may be in a supercritical state at a temperature of atleast 31 °C and pressure of at least 7.4 MPa. The impregnation step S5 may involve having the carbon dioxide in a liquid state, for example by pressurizing the vessel to 20 - 150 bar at a temperature of 5 — 30°C (i.e. below the critical temperature).

The reactor vessel is kept under pressure and temperature control for 6 — 10 h. The composition inside the vessel may be stirred during this time.

When the vessel has a viewing window, the liquid or supercritical state of at least the carbon dioxide can be observed visually. Carbon dioxide in supercritical state has a foggy appearance.

Drying step 96

The vessel may be depressurized to commence drying the produced conductive catalytic particles.

Carbon dioxide is allowed to evaporate, via the outlet 47 and/or by opening the openable cover 42 of the reactor 40.

Drying may also include evaporation of any co-solvents e.g. small molecule alcohols as listed above and/or water). However, co-solvents may also remain, to provide a catalytic formulation that could, for example. be employed as a catalytic ink.

Claims

CONCLUSIONS

1. A method of producing conductive catalytic particles for heterogeneous catalysis, comprising: - a providing step (S1) of providing in a vessel porous particles comprising a porous support material carrying a catalyst material; and - an impregnation step (S35) of exposing in the vessel the porous particles to an impregnation solution comprising a conductive polymer in carbon dioxide, whereby the porous particles are impregnated with the conductive polymer to obtain the conductive catalytic particles.

2. The method of claim 1, wherein the impregnation step (S5) comprises controlling temperature and pressure in the vessel to have the carbon dioxide of the impregnation solution in a liquid or supercritical state.

The method of claim 1 or 2, further comprising a drying step (S6) of drying the obtained conductive catalytic particles.

4. The method of any preceding claim, wherein the providing step (S1) comprises a synthesis step (S2) of providing the porous support material in the vessel and exposing the porous support material in the vessel to a catalyst impregnation solution comprising the catalyst material in carbon dioxide, thereby producing the porous particles comprising the porous support material carrying the catalyst material.

5. The method of claim 4, wherein the synthesis step (52) comprises controlling temperature and pressure in the vessel to have the carbon dioxide of the catalyst impregnation solution in a liquid or supercritical state.

6. The method of any preceding claim, wherein the providing step (S1) comprises an activation step (S4) of activating the catalyst material carried by the porous support material in the porous particles.

The method of claim 6, wherein the activation step (S4) comprises calcination or reduction of the catalyst material carried by the porous support material in the porous particles.

8. The method of any preceding claim, wherein the porous support material is formed from a porous carbon, preferably in the form of activated carbon or graphene, or a porous metal oxide, preferably selected from oxides comprising silicon, aluminium, zinc, tin, cerium, one or more transition metals such as titanium and zirconium, or combinations thereof, or a porous inorganic material.

9. The method of any preceding claim, wherein the catalyst material is a metal-based catalyst, preferably comprising Pt, Pd or Ni.

10. The method of any preceding claim, wherein the conducting polymer is a tonomer, in particular selected from anion exchange ionomers or cation exchange ionomers typically used in producing membrane separations for electrochemical cells.

11. Conductive catalytic particle for heterogeneous catalysis obtainable by the method according to any of claims 1 to 10.

12. The conductive catalytic particle of claim 11 comprising a porous support material, a catalyst material and a conductive polymer.

13. The conductive catalytic particle of claim 11 or 12, wherein the porous support material is formed from a porous carbon, preferably in the form of activated carbon or graphene, or a porous metal oxide, preferably selected from a group comprising silica, alumina, zinc oxide and cerium oxide, or a porous inorganic material.

14. The conductive catalytic particle of any one of claims 11 to 13, wherein the catalyst material is a metal-based catalyst, preferably comprising Pt, Pd or Ni.

15. The conducting catalytic particle of any one of claims 11 to 14, wherein the conducting polymer is an ionomer, in particular selected from anion exchange ionomers or cation exchange ionomers typically used in producing membrane separations for electrochemical cells.

16. A conductive catalytic particle of any one of claims 11 to 15, having a cross-sectional size in the range of from 0.1 µm to 1-107 µm, preferably from 1 µm to 1-107 µm, more preferably from 1 µm to 50 µm, as measured by electron microscopy.

17. A conducting catalytic particle of any one of claims 11 to 16 having a cross-section with a roundness in the range of from 0.3 to 1, preferably from 0.5 to 1, more preferably from 0.7 to 1, wherein roundness is calculated as r/R where r is the inscribed circular radius and R is the circumscribed circular radius of the cross-section as measured by electron microscopy.

18. A catalytic formulation comprising conductive catalytic particles according to any one of claims 11 to 17.

19. A catalyst-coated membrane comprising a membrane having at least one side provided with conductive catalytic particles of any one of claims 11 to 17 or the catalytic formulation of claim 18.

20. The catalyst-coated membrane of claim 19, wherein the membrane is formed with a conductive polymer corresponding to the conductive polymer of the conductive catalytic particle.

21. An electrochemical cell comprising two electrodes separated by a catalyst-coated membrane according to claim 19 or 20.

22. The electrochemical cell of claim 21, wherein the electrochemical cell is a fuel cell, electrolyzer or electrolytic cell.

23. Use of conductive catalytic particles according to any of claims 11 to 17 in the manufacture of a heterogeneous catalytic material, a catalytic formulation, a catalytic ink, a catalyst-coated membrane and/or an electrochemical cell.